Will using upload speed limit my download speed?

Forums › Spark New Zealand (including Skinny and BigPipe) › Will using upload speed limit my download speed?

aboylikedave

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#146788 29-May-2014 10:11

HI there

I have just started to backup my computer (iMac) to an online backup service (Backblaze). Whilst it performs the initial backup it is naturally maxing out my upload speed (although this is configurable).

However, this upload seems to be restricting (slowing) my download. Using Backblaze's own bandwidth test my available download bandwidth from their server reduces from 4.2Mbps to 1.2 Mbps when the backup upload is turned on.

Backblaze say this should not be the case and that some ISPs might impose their own download restrictions in relation to upload.

Telecom say this is not the case.

Can anyone shed some light on what might be happening here?

My EPL football websites: Get the results but hide the score of your team at HidetheScore.net. Compare league positions with wage bills at RealPremierLeague.net.

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#1055704 29-May-2014 10:15

Yes it will, as it will cause packet loss for your reply packets, which tells TCP how quickly it should send the data to you.

andrewNZ

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#1055705 29-May-2014 10:16

Your downloads also require upload bandwidth for things like requests and confirmations. If your upload is saturated, it will more than likely affect downloads and general web browsing.

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#1055716 29-May-2014 10:22

That's how TCP works. Every packet you download requires an OK response (which is an upload). If your upload is already full...

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aboylikedave

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#1055721 29-May-2014 10:27

Ah, of course. Is there a clever way then to prioritise TCP reply packets over my backup?

My EPL football websites: Get the results but hide the score of your team at HidetheScore.net. Compare league positions with wage bills at RealPremierLeague.net.

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#1055724 29-May-2014 10:30

Some CPE's support some sort of QoS. Which could help deproritise your backup solution.

You would need to consult your CPE manual.

jonb

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#1055725 29-May-2014 10:31

If you can configure it to only use say 800kbs upload speed, it won't saturate the upload speed bandwidth so the TCP/IP acknowledgments can be processed without delay.

(not written very well by me from a technical perspective, but should work)

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aboylikedave

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#1055738 29-May-2014 10:46

Great, Backblaze does let you limit upload speed. Could someone advise on what amount of upload bandwidth is best to leave then for TCP reply packets?

My EPL football websites: Get the results but hide the score of your team at HidetheScore.net. Compare league positions with wage bills at RealPremierLeague.net.

timmmay

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#1055745 29-May-2014 10:51

I'd set your upload to use 50 - 80% of your available bandwidth. Reply packets take very little bandwidth, I suspect it's more about latency.

jonb

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#1055748 29-May-2014 10:52

Turn off the backup software, and then do a speedtest. At first try limiting the upload bandwith of the backup software to about 75% of your max upload speed, and see how that effects your download speed (you should have normal download speed still). Can then try tweaking it to 80% of upload speed, but not higher than 90%.

aboylikedave

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#1055754 29-May-2014 10:59

This all sounds good. As an aside I've just done a Speedtest at work and it has upload of 65Mbps. Does that mean if I sneaked (!) my iMac to work it would be 60 times faster to Backup? Would it cause any major tech problems?

My EPL football websites: Get the results but hide the score of your team at HidetheScore.net. Compare league positions with wage bills at RealPremierLeague.net.

Glassboy

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#1055755 29-May-2014 11:00

aboylikedave: HI there

I have just started to backup my computer (iMac) to an online backup service (Backblaze). Whilst it performs the initial backup it is naturally maxing out my upload speed (although this is configurable).

However, this upload seems to be restricting (slowing) my download. Using Backblaze's own bandwidth test my available download bandwidth from their server reduces from 4.2Mbps to 1.2 Mbps when the backup upload is turned on.

Backblaze say this should not be the case and that some ISPs might impose their own download restrictions in relation to upload.

Telecom say this is not the case.

Can anyone shed some light on what might be happening here?

In addition to everyone else's answers you're also using resources on your iMAC and networking equipment (router). No matter what the direction the traffic is, the same things are processing it, so your performance is only as good as the smallest part of the "pipe". If possible throttle the traffic from the Backblaze client itself. That way you won't max out your TCP/IP stack, NIC, router etc.

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timmmay

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#1055776 29-May-2014 11:10

aboylikedave: This all sounds good. As an aside I've just done a Speedtest at work and it has upload of 65Mbps. Does that mean if I sneaked (!) my iMac to work it would be 60 times faster to Backup? Would it cause any major tech problems?

You wouldn't get 65Mbps to your target server, maybe 10Mbps, maybe 20Mbps, maybe only 2Mbps. The only way to tell is to try it, but yes it should be at least a bit faster.

andrewNZ

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#1055780 29-May-2014 11:22

aboylikedave: This all sounds good. As an aside I've just done a Speedtest at work and it has upload of 65Mbps. Does that mean if I sneaked (!) my iMac to work it would be 60 times faster to Backup? Would it cause any major tech problems?

This is something that could lose you your job.

xpd

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#1055784 29-May-2014 11:32

andrewNZ:
aboylikedave: This all sounds good. As an aside I've just done a Speedtest at work and it has upload of 65Mbps. Does that mean if I sneaked (!) my iMac to work it would be 60 times faster to Backup? Would it cause any major tech problems?

This is something that could lose you your job.

Yeah, you might want to consult your IT guys before "sneaking" anything onto the network..... at my last job, we use to notice people abusing (in the companies terms at least) the network pretty quickly and investigate what was happening.

Even after hours....

My boss was fine with me using the network for my own needs (doing an online backup of all my photos) over a weekend but during a business week it was a no no.

XPD / Gavin

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aboylikedave

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#1055829 29-May-2014 11:57

andrewNZ:
aboylikedave: This all sounds good. As an aside I've just done a Speedtest at work and it has upload of 65Mbps. Does that mean if I sneaked (!) my iMac to work it would be 60 times faster to Backup? Would it cause any major tech problems?

This is something that could lose you your job.

Thanks for the advice xpd and AndrewNZ.

My EPL football websites: Get the results but hide the score of your team at HidetheScore.net. Compare league positions with wage bills at RealPremierLeague.net.

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